1. Field of the Invention
The present invention relates to base fabrics for polyurethane-coated fabrics, the polyurethane-coated fabrics and processes for their production, and, in particular, polyurethane-coated fabrics having a good air-permeability and durability, base fabrics for use in the production of such coated fabrics and processes for their production.
Polyurethane-coated fabrics comprise a base fabric which is composed of woven fabrics, knitted fabrics, nonwovens or the like, the base fabric having formed thereon a microporous layer or polyurethane resins. Fine pores or micropores of the polyurethane resin layer insure that air passes through the coated fabrics.
The polyurethane-coated fabrics have been, in general, widely used in the production of fabric products such as rain wears, sports wears, rucksacks and the like, after their polyurethane resin layer was processed to form therein air-permeable pores and to make these pores to be very fine, and then subjected to water repellent finishing and the like to confer thereto a water repellency in addition to an air-permeability.
2. Prior Art
In the past, it is conventional, in the production of the air-permeable polyurethane-coated fabrics of the above-described type, to partly or completely penetrate a solution of polyurethane resins (one-pack polyurethane resin solution) into the fabrics, and then to elute solvents from the penetrated solution by means of an eluent such as water and the like to solidify the polyurethane resin solution. In the production of the coated fabrics according to the said production process, more large amounts of the polyurethane resin solution must be penetrated into the fabrics, if it is intended to increase a peeling strength between the fabrics and the polyurethane layer. However, this process results in a drawback that an air-permeability of the produced coated fabrics is decreased and, in addition, their hand is damaged, since interstices of the fabrics are completely filled with the polyurethane resin. In contrast, in the case that only a small amount of the polyurethane resin solution is penetrated into the base fabrics, another drawback is induced, namely, the resulting coated fabrics have the worst peeling strength and lack in durability, while they exhibit a good air-permeability and hand.
For the purpose of suitably controlling both of an air-permeability and durability, Japanese Patent Application Laid-Open Gazette No. 56-26077 describes a process for the production of air-permeable coated fabrics which utilizes water repellent-finished fabrics, and which comprises discontinuously applying a layer of acrylic polymers onto the water repellent-finished fabrics to form an adhesive layer, and dipping it in an eluent, while the fabrics are inhibited from being penetrated by a one-pack polyurethane resin solution because of their water repellency. The coated fabrics produced according to this process possess relatively satisfiable properties since their air-permeability and hand are insured as a result of discontinuous formation of the adhesive layer of the acrylic polymers. However, contrarily, they are substantially not usable for the practical purposes due to their lower peeling strength of at most 0.4 kg/cm (It is our experiences that wears or similar products need a peeling strength of an order of at least 0.7 kg/cm). This is because the adhesion between the acrylic polymers and the fabrics and that between the acrylic polymers and the polyurethane layer are not so good as that between polyurethane and the fabrics or between polyurethanes and each other. The fact shows that the formation of the adhesive layer has no significant meaning.
In order to insure an increased adhesion between the fabrics and the adhesive layer or between the polyurethane layer and the adhesive layer, it is preferable to also use polyurethanes as the adhesive layer. However, the use of a polyurethane adhesive layer in place of the above-described adhesive layer of the acrylic polymers results in a disappearance of air-permeability, during application of a one-pack polyurethane resin solution onto the fabrics, since the solvent of the resin solution dissolves the adhesive layer thereby gaps of the partly formed adhesive layer are filled with the dissolved adhesive layer. Therefore, the use of polyurethane as the adhesive layer has not become possible in the past.